Aircraft typically include a plurality of flight control surfaces that, when controllably positioned, guide the movement of the aircraft from one destination to another. The number and type of flight control surfaces included in an aircraft may vary, but typically include both primary flight control surfaces and secondary flight control surfaces. The primary flight control surfaces are those that are used to control aircraft movement in the pitch, yaw, and roll axes, and the secondary flight control surfaces are those that are used to influence the lift or drag (or both) of the aircraft. Although some aircraft may include additional control surfaces, the primary flight control surfaces typically include a pair of elevators, a rudder, and a pair of ailerons, and the secondary flight control surfaces typically include a plurality of flaps, slats, and spoilers.
The positions of the aircraft flight control surfaces are typically controlled using a flight control surface actuation system. The flight control surface actuation system, in response to position commands that originate from either the flight crew or an aircraft autopilot, moves the aircraft flight control surfaces to the commanded positions. In most instances, this movement is effected via actuators that are coupled to the flight control surfaces.
Typically, the position commands that originate from the flight crew are supplied via some type of input control mechanism. For example, many aircraft include two yoke and wheel type of mechanisms, one for the pilot and one for the co-pilot. Either mechanism can be used to generate desired flight control surface position commands. More recently, however, aircraft are being implemented with control stick type mechanisms, which may be implemented as either side sticks or center sticks. Most notably in aircraft that employ a fly-by-wire system. Similar to the traditional yoke and wheel mechanisms, it is common to include multiple control stick mechanisms in the cockpit, one for the pilot and one for the co-pilot.
Most control stick mechanisms are implemented with some type of mass balance, such as counterbalance weights, to alleviate a potentially large moment that may exist when an aircraft experiences accelerations resulting from longitudinal and lateral accelerations. These additional counterbalance weights can be undesirable in some instances. For example, the counterbalance weights, when included, are in addition to the mounting, control, and feedback hardware associated with the control stick mechanism. Thus, overall size envelope and weight may increase, which may result in a concomitant increase in costs.
Hence, there is a need for a flight control stick mechanism that is mass balanced, but does not increase, or at least significantly increase, overall control stick size and/or weight. The present invention addresses at least this need.